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Research: Plants need all kinds of light

Published måndag 4 januari 2016 kl 16.59
"That's just chlorophyll in a test tube in a lab"
(1:54 min)
Experiment in how green light affects plants, Photo: Karl-Johan Bergstrand
Experiment in how green light affects plants, Photo: Karl-Johan Bergstrand

Swedish researchers have discovered LED lights are not as useful as some have thought for encouraging the growth of indoor plants.

Research shows that plants grow best with all the colors of the spectrum, and not just red and blue, which some scientists had thought. Which means that the sodium vapor lamps that have been used for the past 40 years are still the most effective.

Karl-Johan Bergstrand is a researcher in plants and illumination at the Swedish University of Agricultural Sciences:

“What we’ve discovered is that the quality of the light, the spectral composition, isn’t really of great importance for photosynthesis,” he tells Swedish Radio’s Science Department. “It’s a common misunderstanding that plants can only use blue and red light, and that’s completely wrong.”

This misunderstanding has led to people in the greenhouse branch putting their hopes on LED lamps, where the different wavelengths of light can be controlled. The idea has been to eliminate unnecessary wavelengths, to optimize growth and save energy.

But current research demonstrates that, to their surprise, plants best utilize light with all the colors, with blue, red, orange, and even green elements.

Karl-Johan Bergstrand says the misunderstanding might be because previous researchers saw that chlorophyll mainly absorbed red and blue light.

“But that’s just chlorophyll in a test tube in a lab,” he says. “A complete plant leaf has a completely different absorption spectrum, which is rather rich in green as well.”

Karl-Johan Bergstrand does say, however, that LED lights do have uses in greenhouses, because they can be used to adjust light wavelengths, which can affect factors like flowering, colors, and the occurrence of taste and bioactive elements in plants.

Our journalism is based on credibility and impartiality. Swedish Radio is independent and not affiliated to any political, religious, financial, public or private interests.
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